Simple LM386 LFO (triangle or sine wave LED flasher)

[antiuser]

I've been looking everywhere for this and whatever I find is way over my head or too difficult to isolate just the bit I want.

To put it simply: I have a LM386 dual op-amp and I know it's possible to get at least a triangle if not a sine wave out of it and use it to flash a bog standard 3mm LED along. I just can't seem to find a schematic for a circuit that does *just that*.

If anyone here could post or point me to one, I would be very grateful.

[bluebunny]

I have a LM386 dual op-amp

LM386 is an audio power amplifier. 

[antiuser]

It's an op amp, which is also used to build oscillators, which is what I'm asking about. It's usually good manners to not say anything at all if you're not actually looking to add to a conversation.

[antonis]

I have a LM386 dual op-amp

It's usually good manners to not say anything at all if you're not actually looking to add to a conversation.

I totally agree about good manners so plz delete the whole thread, 'cause there isn't an actual basis for conversation..!! 

http://www.ti.com/lit/ds/symlink/lm386.pdf

[iainpunk]

the problem with the lm386 is that it has some unusual biasing going on, which makes it really hard to make a LFO with it. also lm386 is a single op amp, not a dual.

i suggest an lm358 or tl072 instead, they have more useful characteristics for LFO's, from there on, google is your friend

[deadastronaut]

Do you mean sound to light?...the 386 is an amplifier, not an opamp.

If you want LFO use a tl072 as suggested. 

If you want to use the 386 to light an led when you play, search  " sound to light"  I made a vero of it years ago.

Good luck.

[antonis]

So, did we settle on "conversationally_good_manners_behavior" ..?? 

[antiuser]

The data sheet for the LM386 calls it an op amp. But whatever, if there's no helping, then close the thread.

[antonis]

The data sheet for the LM386 calls it an op amp.

Does also datasheet includes more hidden names, like Myriam or Eugene..?? 

[patrick398]

The data sheet for the LM386 calls it an op amp. But whatever, if there's no helping, then close the thread.

Jeez, from what i can see several people have offered help. No point being stroppy about it, folks around here are incredibly helpful and patient. They're taking time out of their day to help, for free. Worth remembering

[amz-fx]

I have not tried this but it should work. The C value needs to be much larger for an LFO. As shown, I think it is 1kHz



Best regards, Jack

[iainpunk]

The data sheet for the LM386 calls it an op amp. But whatever, if there's no helping, then close the thread.

yes, the 386 is an op amp, but an odd one because the gain is really low and the input is supposed to be biassed different than conventional op amps. some circuits like output power amps are easy to design with this op amp, other things like LFO's are hard to design with this opamp.

[Marcos - Munky]

I have a LM386 dual op-amp

It's usually good manners to not say anything at all if you're not actually looking to add to a conversation.

April's fool, right? Right?

[PRR]

> The data sheet for the LM386 calls it an op amp.

Page 7.
http://www.ti.com/lit/ds/symlink/lm386.pdf
Keep reading:

The bottom plan is what amz-fx used. It makes a Square. (And a triangle, at high Z, which needs a buffer, but sadly the LM386 is a single.)

The top plan tends to be a Sine. If low THD is not required (as for LED fade-in/out) then the lamp may be a few hundred ohm resistor.

[ElectricDruid]

Title of that datasheet:

"LM386 Low Voltage Audio Power Amplifier"

First line of the description:

"The LM386M-1 and LM386MX-1 are power amplifiers"

[rockola]

Title of that datasheet:

"LM386 Low Voltage Audio Power Amplifier"

First line of the description:

"The LM386M-1 and LM386MX-1 are power amplifiers"

In OPs defence, on page 7 it also says
"8.4 Device Functional Modes
As this is an Op Amp ..."

[amz-fx]

It makes a Square. (And a triangle, at high Z, which needs a buffer, but sadly the LM386 is a single.)

True, but the OP only wants to flash an LED, so being high-Z should not be a problem. OP can connect a 22k resistor and 3mm blue LED to the point that I have marked as Triangle and it should be blinky enough. 

regards, Jack

[deadastronaut]

The data sheet for the LM386 calls it an op amp. But whatever, if there's no helping, then close the thread.

this?

https://www.instructables.com/id/Using-LM386-as-an-Oscillator/

[duck_arse]

I don't f%#@ with op amps so this is kinda outside my wheelhouse .....

my manners are too good to say anything, so I'll just watch instead.

[amz-fx]

True, but the OP only wants to flash an LED, so being high-Z should not be a problem. OP can connect a 22k resistor and 3mm blue LED to the point that I have marked as Triangle and it should be blinky enough. 

I breadboarded the circuit and the triangle junction does not have a high enough voltage to turn on the LED. I tried blue, red and green devices with a variety of resistor values.

You can drive an LED from the Square wave output. A video of it is in my Instagram, and the schematic is in my blog: http://www.muzique.com/news/

Best regards, Jack